1. Field
The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device capable of minimizing a decrease in light emission efficiency at high currents.
2. Description of the Related Art
A light emitting diode (LED) is a semiconductor device that can emit light of various colors due to electron-hole recombination occurring at a p-n junction when a current is applied thereto. Compared to conventional lighting sources such as incandescent lighting bulbs and fluorescent lamps, LED has many advantages such as a long lifespan, low power, excellent initial-operation characteristics, and high tolerance to repetitive power on/off. Hence the demand for LED is continuously increasing. Particularly, group III nitride semiconductors that can emit light in the blue/short wavelength region have recently drawn much attention.
However, in a light emitting device using the group III nitride semiconductor, electrons that have a higher mobility than holes flow to a p-type semiconductor layer without combining with the holes. This, as shown in FIG. 1, causes an electron leakage current to increase as the magnitude of currents being injected increases. The increase in the electron leakage current is called electron overflow. FIG. 1 is a graph showing a change in the electron leakage current according to injection currents in a related art nitride semiconductor light emitting device.
The electron leakage current decreases quantum efficiency, and is becoming a more crucial limitation because LEDs are increasingly being used at high currents as in lighting devices. However, no methods have been proposed to completely overcome this limitation. Therefore, there is a need for a high-efficiency nitride semiconductor light emitting device that has high quantum efficiency in every current region, especially at high currents, and thus can be used for a lighting device or the like.